1. Field of the Invention
The present invention pertains to a trigger sprayer containing a valve element that, while the pump is being primed, vents air from a pump chamber of the sprayer to the interior of a liquid container to which the sprayer is attached.
2. Description of the Related Art
A pressure buildup sprayer is a general category of sprayer in which liquid dispensed from the sprayer is first raised to a certain pressure level before it is dispensed from the sprayer. Typically, sprayers of this type contain a manually operable pump that draws liquid from a container to which the sprayer is attached, and dispenses the liquid from a nozzle orifice of the sprayer. Positioned within the sprayer between the pump and the nozzle orifice is a pressure regulator or pressure buildup valve that regulates the pressure of the liquid dispensed from the nozzle orifice. In operation, as liquid is drawn from the container to the pump and is then made to flow from the pump toward the nozzle orifice in response to actuation of the pump, a pressure regulator positioned in the liquid flow path between the pump and nozzle orifice prevents the flow of liquid to the orifice until the liquid is raised to a certain pressure level at which the regulator opens communication to the nozzle orifice and the liquid is dispensed from the sprayer.
In prior art pressure buildup sprayers, difficulties are frequently encountered in first priming the pump of the sprayer with liquid from the container to which it is attached. In priming the sprayer pump, air in the pump chamber must be displaced as liquid from the container is drawn into the pump chamber. However, due to the compressibility of the air in the pump chamber, it is often difficult to raise the pressure of the air by actuation of the sprayer pump to the level required to open the pressure regulator and permit the air to be displaced from the pump chamber and through the pressure regulator and the nozzle orifice. Frequently, the biasing force of the pressure regulator valve in prior art pressure buildup sprayers is too large to be overcome by the increased pressure of the air in the pump chamber when priming the pump due to the compressibility of the air.